JVET coding block structure with asymmetrical partitioning

ABSTRACT

A method of partitioning a video coding block for JVET, comprising representing a JVET coding tree unit as a root node in a quadtree plus binary tree (QTBT) structure that can have a quadtree branching from the root node and binary trees branching from each of the quadtree&#39;s leaf nodes using asymmetric binary partitioning to split a coding unit represented by a quadtree leaf node into two child coding units of unequal size, representing the two child coding units as leaf nodes in a binary tree branching from the quadtree leaf node and coding the child coding units represented by leaf nodes of the binary tree with JVET, wherein further partitioning of child coding units split from quadtree leaf nodes via asymmetric binary partitioning is disallowed.

CLAIM OF PRIORITY

This application claims priority to U.S. patent application Ser. No.15/605,150 filed May 25, 2017 which claims the benefit of U.S.Provisional Application Ser. No. 62/341,325 filed May 25, 2016, all ofwhich is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to the field of video coding,particularly a block partitioning scheme for JVET that allows quadtreepartitioning, symmetric binary partitioning, and asymmetric binarypartitioning in a quadtree plus binary tree (QTBT) structure.

BACKGROUND

The technical improvements in evolving video coding standards illustratethe trend of increasing coding efficiency to enable higher bit-rates,higher resolutions, and better video quality. The Joint VideoExploration Team is developing a new video coding scheme referred to asJVET. Similar to other video coding schemes like HEVC (High EfficiencyVideo Coding), JVET is a block-based hybrid spatial and temporalpredictive coding scheme. However, relative to HEVC, JVET includes manymodifications to bitstream structure, syntax, constraints, and mappingfor the generation of decoded pictures. JVET has been implemented inJoint Exploration Model (JEM) encoders and decoders.

SUMMARY

The present disclosure provides a method of partitioning a video codingblock for JVET, the method comprising representing a JVET coding treeunit as a root node in a quadtree plus binary tree (QTBT) structure thatcan have a quadtree branching from the root node and binary treesbranching from each of the quadtree's leaf nodes using asymmetric binarypartitioning to split a coding unit represented by a quadtree leaf nodeinto two child coding units of unequal size, representing the two childcoding units as leaf nodes in a binary tree branching from the quadtreeleaf node and coding the child coding units represented by leaf nodes ofthe binary tree with JVET, wherein further partitioning of child codingunits split from quadtree leaf nodes via asymmetric binary partitioningis disallowed.

The present disclosure also provides a method of partitioning a videocoding block for JVET, the method comprising representing a JVET codingtree unit as a root node in a quadtree plus binary tree (QTBT) structurethat can have a quadtree branching from the root node and binary treesbranching from each of the quadtree's leaf nodes, splitting a squareblock represented by a quadtree node with quadtree partitioning intofour square blocks of equal size and representing them as quadtree nodesthat can represent final coding units or be split again with quadtreepartitioning, symmetric binary partitioning, or asymmetric binarypartitioning, with symmetric binary partitioning into two blocks ofequal size and representing them in a binary tree branching from thequadtree node as child nodes that can represent final coding units or berecursively split again with symmetric binary partitioning, or withasymmetric binary partitioning into two blocks of unequal size andrepresenting them in a binary tree branching from the quadtree node asleaf nodes that represents final coding units and for which furthersplitting is disallowed, and coding the coding units represented by leafnodes of the QTBT structure with JVET.

The present disclosure also provides a method of decoding a JVETbitstream, the method comprising receiving a bitstream indicating how acoding tree unit was partitioned into coding units according to aquadtree plus binary tree (QTBT) structure that allows quadtree nodes tobe split with quadtree partitioning, symmetric binary partitioning, orasymmetric binary partitioning, identifying coding units represented byleaf nodes of the QTBT structure, wherein an indication that a node wassplit from a quadtree leaf node using asymmetric binary partitioningdirectly indicates that the node represents a final coding unit to bedecoded, and decoding the identified coding units using JVET.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the present invention are explained with the help ofthe attached drawings in which:

FIG. 1 depicts division of a frame into a plurality of Coding Tree Units(CTUs).

FIG. 2 depicts an exemplary partitioning of a CTU into Coding Units(CUs) using quadtree partitioning and symmetric binary partitioning.

FIG. 3 depicts a quadtree plus binary tree (QTBT) representation of FIG.2 's partitioning.

FIG. 4 depicts four possible types of asymmetric binary partitioning ofa CU into two smaller CUs.

FIG. 5 depicts an exemplary partitioning of a CTU into CUs usingquadtree partitioning, symmetric binary partitioning, and asymmetricbinary partitioning.

FIG. 6 depicts a QTBT representation of FIG. 5 's partitioning.

FIG. 7 depicts a simplified block diagram for CU coding in a JVETencoder.

FIG. 8 depicts 67 possible intra prediction modes for luma components inJVET.

FIG. 9 depicts a simplified block diagram for CU coding in a JVETencoder.

FIG. 10 depicts an embodiment of a method of CU coding in a JVETencoder.

FIG. 11 depicts a simplified block diagram for CU coding in a JVETencoder.

FIG. 12 depicts a simplified block diagram for CU decoding in a JVETdecoder.

FIG. 13 depicts an embodiment of a computer system adapted and/orconfigured to process a method of CU coding.

FIG. 14 depicts an embodiment of a coder/decoder system for CUcoding/decoding in a JVET encoder/decoder.

DETAILED DESCRIPTION

FIG. 1 depicts division of a frame into a plurality of Coding Tree Units(CTUs) 100. A frame can be an image in a video sequence. A frame caninclude a matrix, or set of matrices, with pixel values representingintensity measures in the image. Thus, a set of these matrices cangenerate a video sequence. Pixel values can be defined to representcolor and brightness in full color video coding, where pixels aredivided into three channels. For example, in a YCbCr color space pixelscan have a luma value, Y, that represents gray level intensity in theimage, and two chrominance values, Cb and Cr, that represent the extentto which color differs from gray to blue and red. In other embodiments,pixel values can be represented with values in different color spaces ormodels. The resolution of the video can determine the number of pixelsin a frame. A higher resolution can mean more pixels and a betterdefinition of the image, but can also lead to higher bandwidth, storage,and transmission requirements.

Frames of a video sequence can be encoded and decoded using JVET. JVETis a video coding scheme being developed by the Joint Video ExplorationTeam. Versions of JVET have been implemented in JEM (Joint ExplorationModel) encoders and decoders. Similar to other video coding schemes likeHEVC (High Efficiency Video Coding), JVET is a block-based hybridspatial and temporal predictive coding scheme. During coding with JVET,a frame is first divided into square blocks called CTUs 100, as shown inFIG. 1 . For example, CTUs 100 can be blocks of 128×128 pixels.

FIG. 2 depicts an exemplary partitioning of a CTU 100 into CUs 102. EachCTU 100 in a frame can be partitioned into one or more CUs (CodingUnits) 102. CUs 102 can be used for prediction and transform asdescribed below. Unlike HEVC, in JVET the CUs 102 can be rectangular orsquare, and can be coded without further partitioning into predictionunits or transform units. The CUs 102 can be as large as their root CTUs100, or be smaller subdivisions of a root CTU 100 as small as 4×4blocks.

In JVET, a CTU 100 can be partitioned into CUs 102 according to aquadtree plus binary tree (QTBT) scheme in which the CTU 100 can berecursively split into square blocks according to a quadtree, and thosesquare blocks can then be recursively split horizontally or verticallyaccording to binary trees. Parameters can be set to control splittingaccording to the QTBT, such as the CTU size, the minimum sizes for thequadtree and binary tree leaf nodes, the maximum size for the binarytree root node, and the maximum depth for the binary trees.

In some embodiments JVET can limit binary partitioning in the binarytree portion of a QTBT to symmetric partitioning, in which blocks can bedivided in half either vertically or horizontally along a midline.

By way of a non-limiting example, FIG. 2 shows a CTU 100 partitionedinto CUs 102, with solid lines indicating quadtree splitting and dashedlines indicating symmetric binary tree splitting. As illustrated, thebinary splitting allows symmetric horizontal splitting and verticalsplitting to define the structure of the CTU and its subdivision intoCUs.

FIG. 3 shows a QTBT representation of FIG. 2 's partitioning. A quadtreeroot node represents the CTU 100, with each child node in the quadtreeportion representing one of four square blocks split from a parentsquare block. The square blocks represented by the quadtree leaf nodescan then be divided symmetrically zero or more times using binary trees,with the quadtree leaf nodes being root nodes of the binary trees. Ateach level of the binary tree portion, a block can be dividedsymmetrically, either vertically or horizontally. A flag set to “0”indicates that the block is symmetrically split horizontally, while aflag set to “1” indicates that the block is symmetrically splitvertically.

In other embodiments JVET can allow either symmetric binary partitioningor asymmetric binary partitioning in the binary tree portion of a QTBT.Asymmetrical motion partitioning (AMP) was allowed in a differentcontext in HEVC when partitioning prediction units (PUs). However, forpartitioning CUs 102 in JVET according to a QTBT structure, asymmetricbinary partitioning can lead to improved partitioning relative tosymmetric binary partitioning when correlated areas of a CU 102 are notpositioned on either side of a midline running through the center of theCU 102. By way of a non-limiting example, when a CU 102 depicts oneobject proximate to the CU's center and another object at the side ofthe CU 102, the CU 102 can be asymmetrically partitioned to put eachobject in separate smaller CUs 102 of different sizes.

FIG. 4 depicts four possible types of asymmetric binary partitioning inwhich a CU 102 is split into two smaller CU 102 along a line runningacross the length or height of the CU 102, such that one of the smallerCUs 102 is 25% of the size of the parent CU 102 and the other is 75% ofthe size of the parent CU 102. The four types of asymmetric binarypartitioning shown in FIG. 4 allow a CU 102 to be split along a line 25%of the way from the left side of the CU 102, 25% of the way from theright side of the CU 102, 25% of the way from the top of the CU 102, or25% of the way from the bottom of the CU 102. In alternate embodimentsan asymmetric partitioning line at which a CU 102 is split can bepositioned at any other position such the CU 102 is not dividedsymmetrically in half.

FIG. 5 depicts a non-limiting example of a CTU 100 partitioned into CUs102 using a scheme that allows both symmetric binary partitioning andasymmetric binary partitioning in the binary tree portion of a QTBT. InFIG. 5 , dashed lines show asymmetric binary partitioning lines, inwhich a parent CU 102 was split using one of the partitioning typesshown in FIG. 4 .

FIG. 6 shows a QTBT representation of FIG. 5 's partitioning. In FIG. 6, two solid lines extending from a node indicates symmetric partitioningin the binary tree portion of a QTBT, while two dashed lines extendingfrom a node indicates asymmetric partitioning in the binary treeportion.

Syntax can be coded in the bitstream that indicates how a CTU 100 waspartitioned into CUs 102. By way of a non-limiting example, syntax canbe coded in the bitstream that indicates which nodes were split withquadtree partitioning, which were split with symmetric binarypartitioning, and which were split with asymmetric binary partitioning.Similarly, syntax can be coded in the bitstream for nodes split withasymmetric binary partitioning that indicates which type of asymmetricbinary partitioning was used, such as one of the four types shown inFIG. 4 .

In some embodiments the use of asymmetric partitioning can be limited tosplitting CUs 102 at the leaf nodes of the quadtree portion of a QTBT.In these embodiments, CUs 102 at child nodes that were split from aparent node using quadtree partitioning in the quadtree portion can befinal CUs 102, or they can be further split using quadtree partitioning,symmetric binary partitioning, or asymmetric binary partitioning. Childnodes in the binary tree portion that were split using symmetric binarypartitioning can be final CUs 102, or they can be further splitrecursively one or more times using symmetric binary partitioning only.Child nodes in the binary tree portion that were split from a QT leafnode using asymmetric binary partitioning can be final CUs 102, with nofurther splitting permitted.

In these embodiments, limiting the use of asymmetric partitioning tosplitting quadtree leaf nodes can reduce search complexity and/or limitoverhead bits. Because only quadtree leaf nodes can be split withasymmetric partitioning, the use of asymmetric partitioning can directlyindicate the end of a branch of the QT portion without other syntax orfurther signaling. Similarly, because asymmetrically partitioned nodescannot be split further, the use of asymmetric partitioning on a nodecan also directly indicate that its asymmetrically partitioned childnodes are final CUs 102 without other syntax or further signaling.

In alternate embodiments, such as when limiting search complexity and/orlimiting the number of overhead bits is less of a concern, asymmetricpartitioning can be used to split nodes generated with quadtreepartitioning, symmetric binary partitioning, and/or asymmetric binarypartitioning.

After quadtree splitting and binary tree splitting using either QTBTstructure described above, the blocks represented by the QTBT's leafnodes represent the final CUs 102 to be coded, such as coding usinginter prediction or intra prediction. For slices or full frames codedwith inter prediction, different partitioning structures can be used forluma and chroma components. For example, for an inter slice a CU 102 canhave Coding Blocks (CBs) for different color components, such as such asone luma CB and two chroma CBs. For slices or full frames coded withintra prediction, the partitioning structure can be the same for lumaand chroma components.

In alternate embodiments JVET can use a two-level coding block structureas an alternative to, or extension of, the QTBT partitioning describedabove. In the two-level coding block structure, a CTU 100 can first bepartitioned at a high level into base units (BUs). The BUs can then bepartitioned at a low level into operating units (OUs).

In embodiments employing the two-level coding block structure, at thehigh level a CTU 100 can be partitioned into BUs according to one of theQTBT structures described above, or according to a quadtree (QT)structure such as the one used in HEVC in which blocks can only be splitinto four equally sized sub-blocks. By way of a non-limiting example, aCTU 102 can be partitioned into BUs according to the QTBT structuredescribed above with respect to FIGS. 5-6 , such that leaf nodes in thequadtree portion can be split using quadtree partitioning, symmetricbinary partitioning, or asymmetric binary partitioning. In this example,the final leaf nodes of the QTBT can be BUs instead of CUs.

At the lower level in the two-level coding block structure, each BUpartitioned from the CTU 100 can be further partitioned into one or moreOUs. In some embodiments, when the BU is square, it can be split intoOUs using quadtree partitioning or binary partitioning, such assymmetric or asymmetric binary partitioning. However, when the BU is notsquare, it can be split into OUs using binary partitioning only.Limiting the type of partitioning that can be used for non-square BUscan limit the number of bits used to signal the type of partitioningused to generate BUs.

Although the discussion below describes coding CUs 102, BUs and OUs canbe coded instead of CUs 102 in embodiments that use the two-level codingblock structure. By way of a non-limiting examples, BUs can be used forhigher level coding operations such as intra prediction or interprediction, while the smaller OUs can be used for lower level codingoperations such as transforms and generating transform coefficients.Accordingly, syntax for be coded for BUs that indicate whether they arecoded with intra prediction or inter prediction, or informationidentifying particular intra prediction modes or motion vectors used tocode the BUs. Similarly, syntax for OUs can identify particulartransform operations or quantized transform coefficients used to codethe OUs.

FIG. 7 depicts a simplified block diagram for CU coding in a JVETencoder. The main stages of video coding include partitioning toidentify CUs 102 as described above, followed by encoding CUs 102 usingprediction at 704 or 706, generation of a residual CU 710 at 708,transformation at 712, quantization at 716, and entropy coding at 720.The encoder and encoding process illustrated in FIG. 7 also includes adecoding process that is described in more detail below.

Given a current CU 102, the encoder can obtain a prediction CU 702either spatially using intra prediction at 704 or temporally using interprediction at 706. The basic idea of prediction coding is to transmit adifferential, or residual, signal between the original signal and aprediction for the original signal. At the receiver side, the originalsignal can be reconstructed by adding the residual and the prediction,as will be described below. Because the differential signal has a lowercorrelation than the original signal, fewer bits are needed for itstransmission.

A slice, such as an entire picture or a portion of a picture, codedentirely with intra-predicted CUs 102 can be an I slice that can bedecoded without reference to other slices, and as such can be a possiblepoint where decoding can begin. A slice coded with at least someinter-predicted CUs can be a predictive (P) or bi-predictive (B) slicethat can be decoded based on one or more reference pictures. P slicesmay use intra-prediction and inter-prediction with previously codedslices. For example, P slices may be compressed further than theI-slices by the use of inter-prediction, but need the coding of apreviously coded slice to code them. B slices can use data from previousand/or subsequent slices for its coding, using intra-prediction orinter-prediction using an interpolated prediction from two differentframes, thus increasing the accuracy of the motion estimation process.In some cases P slices and B slices can also or alternately be encodedusing intra block copy, in which data from other portions of the sameslice is used.

As will be discussed below, intra prediction or inter prediction can beperformed based on reconstructed CUs 734 from previously coded CUs 102,such as neighboring CUs 102 or CUs 102 in reference pictures.

When a CU 102 is coded spatially with intra prediction at 704, an intraprediction mode can be found that best predicts pixel values of the CU102 based on samples from neighboring CUs 102 in the picture.

When coding a CU's luma component, the encoder can generate a list ofcandidate intra prediction modes. While HEVC had 35 possible intraprediction modes for luma components, in NET there are 67 possible intraprediction modes for luma components. These include a planar mode thatuses a three dimensional plane of values generated from neighboringpixels, a DC mode that uses values averaged from neighboring pixels, andthe 65 directional modes shown in FIG. 8 that use values copied fromneighboring pixels along the indicated directions.

When generating a list of candidate intra prediction modes for a CU'sluma component, the number of candidate modes on the list can depend onthe CU's size. The candidate list can include: a subset of HEVC's 35modes with the lowest SATD (Sum of Absolute Transform Difference) costs;new directional modes added for NET that neighbor the candidates foundfrom the HEVC modes; and modes from a set of six most probable modes(MPMs) for the CU 102 that are identified based on intra predictionmodes used for previously coded neighboring blocks as well as a list ofdefault modes.

When coding a CU's chroma components, a list of candidate intraprediction modes can also be generated. The list of candidate modes caninclude modes generated with cross-component linear model projectionfrom luma samples, intra prediction modes found for luma CBs inparticular collocated positions in the chroma block, and chromaprediction modes previously found for neighboring blocks. The encodercan find the candidate modes on the lists with the lowest ratedistortion costs, and use those intra prediction modes when coding theCU's luma and chroma components. Syntax can be coded in the bitstreamthat indicates the intra prediction modes used to code each CU 102.

After the best intra prediction modes for a CU 102 have been selected,the encoder can generate a prediction CU 402 using those modes. When theselected modes are directional modes, a 4-tap filter can be used toimprove the directional accuracy. Columns or rows at the top or leftside of the prediction block can be adjusted with boundary predictionfilters, such as 2-tap or 3-tap filters.

The prediction CU 702 can be smoothed further with a position dependentintra prediction combination (PDPC) process that adjusts a prediction CU702 generated based on filtered samples of neighboring blocks usingunfiltered samples of neighboring blocks, or adaptive reference samplesmoothing using 3-tap or 5-tap low pass filters to process referencesamples.

When a CU 102 is coded temporally with inter prediction at 706, a set ofmotion vectors (MVs) can be found that points to samples in referencepictures that best predict pixel values of the CU 102. Inter predictionexploits temporal redundancy between slices by representing adisplacement of a block of pixels in a slice. The displacement isdetermined according to the value of pixels in previous or followingslices through a process called motion compensation. Motion vectors andassociated reference indices that indicate pixel displacement relativeto a particular reference picture can be provided in the bitstream to adecoder, along with the residual between the original pixels and themotion compensated pixels. The decoder can use the residual and signaledmotion vectors and reference indices to reconstruct a block of pixels ina reconstructed slice.

In JVET, motion vector accuracy can be stored at 1/16 pel, and thedifference between a motion vector and a CU's predicted motion vectorcan be coded with either quarter-pel resolution or integer-pelresolution.

In JVET motion vectors can be found for multiple sub-CUs within a CU102, using techniques such as advanced temporal motion vector prediction(ATMVP), spatial-temporal motion vector prediction (STMVP), affinemotion compensation prediction, pattern matched motion vector derivation(PMMVD), and/or bi-directional optical flow (BIO).

Using ATMVP, the encoder can find a temporal vector for the CU 102 thatpoints to a corresponding block in a reference picture. The temporalvector can be found based on motion vectors and reference pictures foundfor previously coded neighboring CUs 102. Using the reference blockpointed to by a temporal vector for the entire CU 102, a motion vectorcan be found for each sub-CU within the CU 102.

STMVP can find motion vectors for sub-CUs by scaling and averagingmotion vectors found for neighboring blocks previously coded with interprediction, together with a temporal vector.

Affine motion compensation prediction can be used to predict a field ofmotion vectors for each sub-CU in a block, based on two control motionvectors found for the top corners of the block. For example, motionvectors for sub-CUs can be derived based on top corner motion vectorsfound for each 4×4 block within the CU 102.

PMMVD can find an initial motion vector for the current CU 102 usingbilateral matching or template matching. Bilateral matching can look atthe current CU 102 and reference blocks in two different referencepictures along a motion trajectory, while template matching can look atcorresponding blocks in the current CU 102 and a reference pictureidentified by a template. The initial motion vector found for the CU 102can then be refined individually for each sub-CU.

BIO can be used when inter prediction is performed with bi-predictionbased on earlier and later reference pictures, and allows motion vectorsto be found for sub-CUs based on the gradient of the difference betweenthe two reference pictures.

In some situations local illumination compensation (LIC) can be used atthe CU level to find values for a scaling factor parameter and an offsetparameter, based on samples neighboring the current CU 102 andcorresponding samples neighboring a reference block identified by acandidate motion vector. In JVET, the LIC parameters can change and besignaled at the CU level.

For some of the above methods the motion vectors found for each of aCU's sub-CUs can be signaled to decoders at the CU level. For othermethods, such as PMMVD and BIO, motion information is not signaled inthe bitstream to save overhead, and decoders can derive the motionvectors through the same processes.

After the motion vectors for a CU 102 have been found, the encoder cangenerate a prediction CU 702 using those motion vectors. In some cases,when motion vectors have been found for individual sub-CUs, OverlappedBlock Motion Compensation (OBMC) can be used when generating aprediction CU 702 by combining those motion vectors with motion vectorspreviously found for one or more neighboring sub-CUs.

When bi-prediction is used, JVET can use decoder-side motion vectorrefinement (DMVR) to find motion vectors. DMVR allows a motion vector tobe found based on two motion vectors found for bi-prediction using abilateral template matching process. In DMVR, a weighted combination ofprediction CUs 702 generated with each of the two motion vectors can befound, and the two motion vectors can be refined by replacing them withnew motion vectors that best point to the combined prediction CU 702.The two refined motion vectors can be used to generate the finalprediction CU 702.

At 708, once a prediction CU 702 has been found with intra prediction at704 or inter prediction at 706 as described above, the encoder cansubtract the prediction CU 702 from the current CU 102 find a residualCU 710.

The encoder can use one or more transform operations at 712 to convertthe residual CU 710 into transform coefficients 714 that express theresidual CU 710 in a transform domain, such as using a discrete cosineblock transform (DCT-transform) to convert data into the transformdomain. JVET allows more types of transform operations than HEVC,including DCT-II, DST-VII, DST-VII, DCT-VIII, DST-I, and DCT-Voperations. The allowed transform operations can be grouped intosub-sets, and an indication of which sub-sets and which specificoperations in those sub-sets were used can be signaled by the encoder.In some cases, large block-size transforms can be used to zero out highfrequency transform coefficients in CUs 102 larger than a certain size,such that only lower-frequency transform coefficients are maintained forthose CUs 102.

In some cases a mode dependent non-separable secondary transform(MDNSST) can be applied to low frequency transform coefficients 714after a forward core transform. The MDNSST operation can use aHypercube-Givens Transform (HyGT) based on rotation data. When used, anindex value identifying a particular MDNSST operation can be signaled bythe encoder.

At 716, the encoder can quantize the transform coefficients 714 intoquantized transform coefficients 716. The quantization of eachcoefficient may be computed by dividing a value of the coefficient by aquantization step, which is derived from a quantization parameter (QP).In some embodiments, the Qstep is defined as 2^((QP−4)/6). Because highprecision transform coefficients 714 can be converted into quantizedtransform coefficients 716 with a finite number of possible values,quantization can assist with data compression. Thus, quantization of thetransform coefficients may limit an amount of bits generated and sent bythe transformation process. However, while quantization is a lossyoperation, and the loss by quantization cannot be recovered, thequantization process presents a trade-off between quality of thereconstructed sequence and an amount of information needed to representthe sequence. For example, a lower QP value can result in better qualitydecoded video, although a higher amount of data may be required forrepresentation and transmission. In contrast, a high QP value can resultin lower quality reconstructed video sequences but with lower data andbandwidth needs.

JVET can utilize variance-based adaptive quantization techniques, whichallows every CU 102 to use a different quantization parameter for itscoding process (instead of using the same frame QP in the coding ofevery CU 102 of the frame). The variance-based adaptive quantizationtechniques adaptively lowers the quantization parameter of certainblocks while increasing it in others. To select a specific QP for a CU102, the CU's variance is computed. In brief, if a CU's variance ishigher than the average variance of the frame, a higher QP than theframe's QP may be set for the CU 102. If the CU 102 presents a lowervariance than the average variance of the frame, a lower QP may beassigned.

At 720, the encoder can find final compression bits 722 by entropycoding the quantized transform coefficients 718. Entropy coding aims toremove statistical redundancies of the information to be transmitted. InNET, CABAC (Context Adaptive Binary Arithmetic Coding) can be used tocode the quantized transform coefficients 718, which uses probabilitymeasures to remove the statistical redundancies. For CUs 102 withnon-zero quantized transform coefficients 718, the quantized transformcoefficients 718 can be converted into binary. Each bit (“bin”) of thebinary representation can then be encoded using a context model. A CU102 can be broken up into three regions, each with its own set ofcontext models to use for pixels within that region.

Multiple scan passes can be performed to encode the bins. During passesto encode the first three bins (bin0, bin1, and bin2), an index valuethat indicates which context model to use for the bin can be found byfinding the sum of that bin position in up to five previously codedneighboring quantized transform coefficients 718 identified by atemplate.

A context model can be based on probabilities of a bin's value being ‘0’or ‘1’. As values are coded, the probabilities in the context model canbe updated based on the actual number of ‘0’ and ‘1’ values encountered.While HEVC used fixed tables to re-initialize context models for eachnew picture, in NET the probabilities of context models for newinter-predicted pictures can be initialized based on context modelsdeveloped for previously coded inter-predicted pictures.

The encoder can produce a bitstream that contains entropy encoded bits722 of residual CUs 710, prediction information such as selected intraprediction modes or motion vectors, indicators of how the CUs 102 werepartitioned from a CTU 100 according to the QTBT structure, and/or otherinformation about the encoded video. The bitstream can be decoded by adecoder as discussed below.

In addition to using the quantized transform coefficients 718 to findthe final compression bits 722, the encoder can also use the quantizedtransform coefficients 718 to generate reconstructed CUs 734 byfollowing the same decoding process that a decoder would use to generatereconstructed CUs 734. Thus, once the transformation coefficients havebeen computed and quantized by the encoder, the quantized transformcoefficients 718 may be transmitted to the decoding loop in the encoder.After quantization of a CU's transform coefficients, a decoding loopallows the encoder to generate a reconstructed CU 734 identical to theone the decoder generates in the decoding process. Accordingly, theencoder can use the same reconstructed CUs 734 that a decoder would usefor neighboring CUs 102 or reference pictures when performing intraprediction or inter prediction for a new CU 102. Reconstructed CUs 102,reconstructed slices, or full reconstructed frames may serve asreferences for further prediction stages.

At the encoder's decoding loop (and see below, for the same operationsin the decoder) to obtain pixel values for the reconstructed image, adequantization process may be performed. To dequantize a frame, forexample, a quantized value for each pixel of a frame is multiplied bythe quantization step, e.g., (Qstep) described above, to obtainreconstructed dequantized transform coefficients 726. For example, inthe decoding process shown in FIG. 7 in the encoder, the quantizedtransform coefficients 718 of a residual CU 710 can be dequantized at724 to find dequantized transform coefficients 726. If an MDNSSToperation was performed during encoding, that operation can be reversedafter dequantization.

At 728, the dequantized transform coefficients 726 can be inversetransformed to find a reconstructed residual CU 730, such as by applyinga DCT to the values to obtain the reconstructed image. At 732 thereconstructed residual CU 730 can be added to a corresponding predictionCU 702 found with intra prediction at 704 or inter prediction at 706, inorder to find a reconstructed CU 734.

At 736, one or more filters can be applied to the reconstructed dataduring the decoding process (in the encoder or, as described below, inthe decoder), at either a picture level or CU level. For example, theencoder can apply a deblocking filter, a sample adaptive offset (SAO)filter, and/or an adaptive loop filter (ALF). The encoder's decodingprocess may implement filters to estimate and transmit to a decoder theoptimal filter parameters that can address potential artifacts in thereconstructed image. Such improvements increase the objective andsubjective quality of the reconstructed video. In deblocking filtering,pixels near a sub-CU boundary may be modified, whereas in SAO, pixels ina CTU 100 may be modified using either an edge offset or band offsetclassification. JVET's ALF can use filters with circularly symmetricshapes for each 2×2 block. An indication of the size and identity of thefilter used for each 2×2 block can be signaled.

If reconstructed pictures are reference pictures, they can be stored ina reference buffer 738 for inter prediction of future CUs 102 at 706.

During the above steps, JVET allows a content adaptive clippingoperations to be used to adjust color values to fit between lower andupper clipping bounds. The clipping bounds can change for each slice,and parameters identifying the bounds can be signaled in the bitstream.

FIG. 9 depicts a simplified block diagram for CU coding in a JVETdecoder. A JVET decoder can receive a bitstream containing informationabout encoded CUs 102. The bitstream can indicate how CUs 102 of apicture were partitioned from a CTU 100 according to a QTBT structure.By way of a non-limiting example, the bitstream can identify how CUs 102were partitioned from each CTU 100 in a QTBT using quadtreepartitioning, symmetric binary partitioning, and/or asymmetric binarypartitioning. The bitstream can also indicate prediction information forthe CUs 102 such as intra prediction modes or motion vectors, and bits902 representing entropy encoded residual CUs.

At 904 the decoder can decode the entropy encoded bits 902 using theCABAC context models signaled in the bitstream by the encoder. Thedecoder can use parameters signaled by the encoder to update the contextmodels' probabilities in the same way they were updated during encoding.

After reversing the entropy encoding at 904 to find quantized transformcoefficients 906, the decoder can dequantize them at 908 to finddequantized transform coefficients 910. If an MDNSST operation wasperformed during encoding, that operation can be reversed by the decoderafter dequantization.

At 912, the dequantized transform coefficients 910 can be inversetransformed to find a reconstructed residual CU 914. At 916, thereconstructed residual CU 914 can be added to a corresponding predictionCU 926 found with intra prediction at 922 or inter prediction at 924, inorder to find a reconstructed CU 918.

At 920, one or more filters can be applied to the reconstructed data, ateither a picture level or CU level. For example, the decoder can apply adeblocking filter, a sample adaptive offset (SAO) filter, and/or anadaptive loop filter (ALF). As described above, the in-loop filterslocated in the decoding loop of the encoder may be used to estimateoptimal filter parameters to increase the objective and subjectivequality of a frame. These parameters are transmitted to the decoder tofilter the reconstructed frame at 920 to match the filteredreconstructed frame in the encoder.

After reconstructed pictures have been generated by findingreconstructed CUs 918 and applying signaled filters, the decoder canoutput the reconstructed pictures as output video 928. If reconstructedpictures are to be used as reference pictures, they can be stored in areference buffer 930 for inter prediction of future CUs 102 at 924.

FIG. 10 depicts an embodiment of a method of CU coding 1000 in a JVETdecoder. In the embodiment depicted in FIG. 10 , in step 1002 an encodedbitstream 902 can be received and then in step 1004 the CABAC contextmodel associated with the encoded bitstream 902 can be determined andthe encoded bitstream 902 can then be decoded using the determined CABACcontext model in step 1006.

In step 1008, the quantized transform coefficients 906 associated withthe encoded bitstream 902 can be determined and de-quantized transformcoefficients 910 can then be determined from the quantized transformcoefficients 906 in step 1010.

In step 1012, it can be determined whether an MDNSST operation wasperformed during encoding and/or if the bitstream 902 containsindications that an MDNSST operation was applied to the bitstream 902.If it is determined that an MDNSST operation was performed during theencoding process or the bitstream 902 contains indications that anMDNSST operation was applied to the bitstream 902, then an inverseMDNSST operation 1014 can be implemented before an inverse transformoperation 912 is performed on the bitstream 902 in step 1016.Alternately, an inverse transform operation 912 can be performed on thebitstream 902 in step 1016 absent application of an inverse MDNSSToperation in step 1014. The inverse transform operation 912 in step 1016can determine and/or construct a reconstructed residual CU 914.

In step 1018, the reconstructed residual CU 914 from step 1016 can becombined with a prediction CU 918. The prediction CU 918 can be one ofan intra-prediction CU 922 determined in step 1020 and aninter-prediction unit 924 determined in step 1022.

In step 1024, any one or more filters 920 can be applied to thereconstructed CU 914 and output in step 1026. In some embodimentsfilters 920 may not be applied in step 1024.

In some embodiments, in step 1028, the reconstructed CU 918 can bestored in a reference buffer 930.

FIG. 11 depicts a simplified block diagram 1100 for CU coding in a JVETencoder. In step 1102 a JVET coding tree unit can be represented as aroot node in a quadtree plus binary tree (QTBT) structure. In someembodiments the QTBT can have a quadtree branching from the root nodeand/or binary trees branching from one or more of the quadtree's leafnodes. The representation from step 1102 can proceed to step 1104, 1106or 1108.

In step 1104, asymmetric binary partitioning can be employed to split arepresented quadtree node into two blocks of unequal size. In someembodiments, the split blocks can be represented in a binary treebranching from the quadtree node as leaf nodes that can represent finalcoding units. In some embodiment, the binary tree branching from thequadtree node as leaf nodes represent final coding units in whichfurther splitting is disallowed. In some embodiments the asymmetricpartitioning can split a coding unit into blocks of unequal size, afirst representing 25% of the quadtree node and a second representing75% of the quadtree node.

In step 1106, quadtree partitioning can be employed to split arepresented quadtree note into four square blocks of equal size. In someembodiments the split blocks can be represented as quadtree notes thatrepresent final coding units or can be represented as child nodes thatcan be split again with quadtree partitioning, symmetric binarypartitioning, or asymmetric binary partitioning.

In step 1108 quadtree partitioning can be employed to split arepresented quadtree note into two blocks of equal size. In someembodiments the split blocks can be represented as quadtree notes thatrepresent final coding units or can be represented as child nodes thatcan be split again with quadtree partitioning, symmetric binarypartitioning, or asymmetric binary partitioning.

In step 1110, child nodes from step 1106 or step 1108 can be representedas child coding units configured to be encoded. In some embodiments thechild coding units can be represented by leaf notes of the binary treewith JVET.

In step 1112, coding units from step 1104 or 1110 can be encoded usingJVET.

FIG. 12 depicts a simplified block diagram 1200 for CU decoding in aJVET decoder. In the embodiment depicted in FIG. 12 , in step 1202 abitstream indicating how a coding tree unit was partitioned into codingunits according to a QTBT structure can be received. The bitstream canindicate how quadtree nodes are split with at least one of quadtreepartitioning, symmetric binary partitioning or asymmetric binarypartitioning.

In step 1204, coding units, represented by leaf nodes of the QTBTstructure can be identified. In some embodiments, the coding units canindicate whether a node was split from a quadtree leaf node usingasymmetric binary partitioning. In some embodiments, the coding unit canindicate that the node represents a final coding unit to be decoded.

In step 1206, the identified coding unit(s) can be decoded using JVET.

The execution of the sequences of instructions required to practice theembodiments can be performed by a computer system 1300 as shown in FIG.13 . In an embodiment, execution of the sequences of instructions isperformed by a single computer system 1300. According to otherembodiments, two or more computer systems 1300 coupled by acommunication link 1315 can perform the sequence of instructions incoordination with one another. Although a description of only onecomputer system 1300 will be presented below, however, it should beunderstood that any number of computer systems 1300 can be employed topractice the embodiments.

A computer system 1300 according to an embodiment will now be describedwith reference to FIG. 13 , which is a block diagram of the functionalcomponents of a computer system 1300. As used herein, the term computersystem 1300 is broadly used to describe any computing device that canstore and independently run one or more programs.

Each computer system 1300 can include a communication interface 1314coupled to the bus 1306. The communication interface 1314 providestwo-way communication between computer systems 1300. The communicationinterface 1314 of a respective computer system 1300 transmits andreceives electrical, electromagnetic or optical signals that includedata streams representing various types of signal information, e.g.,instructions, messages and data. A communication link 1315 links onecomputer system 1300 with another computer system 1300. For example, thecommunication link 1315 can be a LAN, in which case the communicationinterface 1314 can be a LAN card, or the communication link 1315 can bea PSTN, in which case the communication interface 1314 can be anintegrated services digital network (ISDN) card or a modem, or thecommunication link 1315 can be the Internet, in which case thecommunication interface 1314 can be a dial-up, cable or wireless modem.

A computer system 1300 can transmit and receive messages, data, andinstructions, including program, i.e., application, code, through itsrespective communication link 1315 and communication interface 1314.Received program code can be executed by the respective processor(s)1307 as it is received, and/or stored in the storage device 1310, orother associated non-volatile media, for later execution.

In an embodiment, the computer system 1300 operates in conjunction witha data storage system 1331, e.g., a data storage system 1331 thatcontains a database 1332 that is readily accessible by the computersystem 1300. The computer system 1300 communicates with the data storagesystem 1331 through a data interface 1333. A data interface 1333, whichis coupled to the bus 1306, transmits and receives electrical,electromagnetic or optical signals, that include data streamsrepresenting various types of signal information, e.g., instructions,messages and data. In embodiments, the functions of the data interface1333 can be performed by the communication interface 1314.

Computer system 1300 includes a bus 1306 or other communicationmechanism for communicating instructions, messages and data,collectively, information, and one or more processors 1307 coupled withthe bus 1306 for processing information. Computer system 1300 alsoincludes a main memory 1308, such as a random access memory (RAM) orother dynamic storage device, coupled to the bus 1306 for storingdynamic data and instructions to be executed by the processor(s) 1307.The main memory 1308 also can be used for storing temporary data, i.e.,variables, or other intermediate information during execution ofinstructions by the processor(s) 1307.

The computer system 1300 can further include a read only memory (ROM)1309 or other static storage device coupled to the bus 1306 for storingstatic data and instructions for the processor(s) 1307. A storage device1310, such as a magnetic disk or optical disk, can also be provided andcoupled to the bus 1306 for storing data and instructions for theprocessor(s) 1307.

A computer system 1300 can be coupled via the bus 1306 to a displaydevice 1311, such as, but not limited to, a cathode ray tube (CRT) or aliquid-crystal display (LCD) monitor, for displaying information to auser. An input device 1312, e.g., alphanumeric and other keys, iscoupled to the bus 1306 for communicating information and commandselections to the processor(s) 1307.

According to one embodiment, an individual computer system 1300 performsspecific operations by their respective processor(s) 1307 executing oneor more sequences of one or more instructions contained in the mainmemory 1308. Such instructions can be read into the main memory 1308from another computer-usable medium, such as the ROM 1309 or the storagedevice 1310. Execution of the sequences of instructions contained in themain memory 1308 causes the processor(s) 1307 to perform the processesdescribed herein. In alternative embodiments, hard-wired circuitry canbe used in place of or in combination with software instructions. Thus,embodiments are not limited to any specific combination of hardwarecircuitry and/or software.

The term “computer-usable medium,” as used herein, refers to any mediumthat provides information or is usable by the processor(s) 1307. Such amedium can take many forms, including, but not limited to, non-volatile,volatile and transmission media. Non-volatile media, i.e., media thatcan retain information in the absence of power, includes the ROM 1309,CD ROM, magnetic tape, and magnetic discs. Volatile media, i.e., mediathat can not retain information in the absence of power, includes themain memory 1308. Transmission media includes coaxial cables, copperwire and fiber optics, including the wires that comprise the bus 1306.Transmission media can also take the form of carrier waves; i.e.,electromagnetic waves that can be modulated, as in frequency, amplitudeor phase, to transmit information signals. Additionally, transmissionmedia can take the form of acoustic or light waves, such as thosegenerated during radio wave and infrared data communications.

In the foregoing specification, the embodiments have been described withreference to specific elements thereof. It will, however, be evidentthat various modifications and changes can be made thereto withoutdeparting from the broader spirit and scope of the embodiments. Forexample, the reader is to understand that the specific ordering andcombination of process actions shown in the process flow diagramsdescribed herein is merely illustrative, and that using different oradditional process actions, or a different combination or ordering ofprocess actions can be used to enact the embodiments. The specificationand drawings are, accordingly, to be regarded in an illustrative ratherthan restrictive sense.

It should also be noted that the present invention can be implemented ina variety of computer systems. The various techniques described hereincan be implemented in hardware or software, or a combination of both.Preferably, the techniques are implemented in computer programsexecuting on programmable computers that each include a processor, astorage medium readable by the processor (including volatile andnon-volatile memory and/or storage elements), at least one input device,and at least one output device. Program code is applied to data enteredusing the input device to perform the functions described above and togenerate output information. The output information is applied to one ormore output devices. Each program is preferably implemented in a highlevel procedural or object oriented programming language to communicatewith a computer system. However, the programs can be implemented inassembly or machine language, if desired. In any case, the language canbe a compiled or interpreted language. Each such computer program ispreferably stored on a storage medium or device (e.g., ROM or magneticdisk) that is readable by a general or special purpose programmablecomputer for configuring and operating the computer when the storagemedium or device is read by the computer to perform the proceduresdescribed above. The system can also be considered to be implemented asa computer-readable storage medium, configured with a computer program,where the storage medium so configured causes a computer to operate in aspecific and predefined manner. Further, the storage elements of theexemplary computing applications can be relational or sequential (flatfile) type computing databases that are capable of storing data invarious combinations and configurations.

FIG. 14 is a high level view of a source device 1412 and destinationdevice 1410 that may incorporate features of the systems and devicesdescribed herein. As shown in FIG. 14 , example video coding system 1410includes a source device 1412 and a destination device 1414 where, inthis example, the source device 1412 generates encoded video data.Accordingly, source device 1412 may be referred to as a video encodingdevice. Destination device 1414 may decode the encoded video datagenerated by source device 1412. Accordingly, destination device 1414may be referred to as a video decoding device. Source device 1412 anddestination device 1414 may be examples of video coding devices.

Destination device 1414 may receive encoded video data from sourcedevice 1412 via a channel 1416. Channel 1416 may comprise a type ofmedium or device capable of moving the encoded video data from sourcedevice 1412 to destination device 1414. In one example, channel 1416 maycomprise a communication medium that enables source device 1412 totransmit encoded video data directly to destination device 1414 inreal-time.

In this example, source device 1412 may modulate the encoded video dataaccording to a communication standard, such as a wireless communicationprotocol, and may transmit the modulated video data to destinationdevice 1414. The communication medium may comprise a wireless or wiredcommunication medium, such as a radio frequency (RF) spectrum or one ormore physical transmission lines. The communication medium may form partof a packet-based network, such as a local area network, a wide-areanetwork, or a global network such as the Internet. The communicationmedium may include routers, switches, base stations, or other equipmentthat facilitates communication from source device 1412 to destinationdevice 1414. In another example, channel 1416 may correspond to astorage medium that stores the encoded video data generated by sourcedevice 1412.

In the example of FIG. 14 , source device 1412 includes a video source1418, video encoder 1420, and an output interface 1422. In some cases,output interface 1428 may include a modulator/demodulator (modem) and/ora transmitter. In source device 1412, video source 1418 may include asource such as a video capture device, e.g., a video camera, a videoarchive containing previously captured video data, a video feedinterface to receive video data from a video content provider, and/or acomputer graphics system for generating video data, or a combination ofsuch sources.

Video encoder 1420 may encode the captured, pre-captured, orcomputer-generated video data. An input image may be received by thevideo encoder 1420 and stored in the input frame memory 1421. Thegeneral purpose processor 1423 may load information from here andperform encoding. The program for driving the general purpose processormay be loaded from a storage device, such as the example memory modulesdepicted in FIG. 14 . The general purpose processor may use processingmemory 1422 to perform the encoding, and the output of the encodinginformation by the general processor may be stored in a buffer, such asoutput buffer 1426.

The video encoder 1420 may include a resampling module 1425 which may beconfigured to code (e.g., encode) video data in a scalable video codingscheme that defines at least one base layer and at least one enhancementlayer. Resampling module 1425 may resample at least some video data aspart of an encoding process, wherein resampling may be performed in anadaptive manner using resampling filters.

The encoded video data, e.g., a coded bit stream, may be transmitteddirectly to destination device 1414 via output interface 1428 of sourcedevice 1412. In the example of FIG. 14 , destination device 1414includes an input interface 1438, a video decoder 1430, and a displaydevice 1432. In some cases, input interface 1428 may include a receiverand/or a modem. Input interface 1438 of destination device 1414 receivesencoded video data over channel 1416. The encoded video data may includea variety of syntax elements generated by video encoder 1420 thatrepresent the video data. Such syntax elements may be included with theencoded video data transmitted on a communication medium, stored on astorage medium, or stored a file server.

The encoded video data may also be stored onto a storage medium or afile server for later access by destination device 1414 for decodingand/or playback. For example, the coded bitstream may be temporarilystored in the input buffer 1431, then loaded in to the general purposeprocessor 1433. The program for driving the general purpose processormay be loaded from a storage device or memory. The general purposeprocessor may use a process memory 1432 to perform the decoding. Thevideo decoder 1430 may also include a resampling module 1435 similar tothe resampling module 1425 employed in the video encoder 1420.

FIG. 14 depicts the resampling module 1435 separately from the generalpurpose processor 1433, but it would be appreciated by one of skill inthe art that the resampling function may be performed by a programexecuted by the general purpose processor, and the processing in thevideo encoder may be accomplished using one or more processors. Thedecoded image(s) may be stored in the output frame buffer 1436 and thensent out to the input interface 1438.

Display device 1438 may be integrated with or may be external todestination device 1414. In some examples, destination device 1414 mayinclude an integrated display device and may also be configured tointerface with an external display device. In other examples,destination device 1414 may be a display device. In general, displaydevice 1438 displays the decoded video data to a user.

Video encoder 1420 and video decoder 1430 may operate according to avideo compression standard. ITU-T VCEG (Q6/16) and ISO/IEC MPEG (JTC1/SC 29/WG 11) are studying the potential need for standardization offuture video coding technology with a compression capability thatsignificantly exceeds that of the current High Efficiency Video CodingHEVC standard (including its current extensions and near-term extensionsfor screen content coding and high-dynamic-range coding). The groups areworking together on this exploration activity in a joint collaborationeffort known as the Joint Video Exploration Team (JVET) to evaluatecompression technology designs proposed by their experts in this area. Arecent capture of JVET development is described in the “AlgorithmDescription of Joint Exploration Test Model 5 (JEM 5)”, JVET-E1001-V2,authored by J. Chen, E. Alshina, G. Sullivan, J. Ohm, J. Boyce.

Additionally or alternatively, video encoder 1420 and video decoder 1430may operate according to other proprietary or industry standards thatfunction with the disclosed JVET features. Thus, other standards such asthe ITU-T H.264 standard, alternatively referred to as MPEG-4, Part 10,Advanced Video Coding (AVC), or extensions of such standards. Thus,while newly developed for JVET, techniques of this disclosure are notlimited to any particular coding standard or technique. Other examplesof video compression standards and techniques include MPEG-2, ITU-TH.263 and proprietary or open source compression formats and relatedformats.

Video encoder 1420 and video decoder 1430 may be implemented inhardware, software, firmware or any combination thereof. For example,the video encoder 1420 and decoder 1430 may employ one or moreprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASICs), field programmable gate arrays (FPGAs),discrete logic, or any combinations thereof. When the video encoder 1420and decoder 1430 are implemented partially in software, a device maystore instructions for the software in a suitable, non-transitorycomputer-readable storage medium and may execute the instructions inhardware using one or more processors to perform the techniques of thisdisclosure. Each of video encoder 1420 and video decoder 1430 may beincluded in one or more encoders or decoders, either of which may beintegrated as part of a combined encoder/decoder (CODEC) in a respectivedevice.

Aspects of the subject matter described herein may be described in thegeneral context of computer-executable instructions, such as programmodules, being executed by a computer, such as the general purposeprocessors 1423 and 1433 described above. Generally, program modulesinclude routines, programs, objects, components, data structures, and soforth, which perform particular tasks or implement particular abstractdata types. Aspects of the subject matter described herein may also bepracticed in distributed computing environments where tasks areperformed by remote processing devices that are linked through acommunications network. In a distributed computing environment, programmodules may be located in both local and remote computer storage mediaincluding memory storage devices.

Examples of memory include random access memory (RAM), read only memory(ROM), or both. Memory may store instructions, such as source code orbinary code, for performing the techniques described above. Memory mayalso be used for storing variables or other intermediate informationduring execution of instructions to be executed by a processor, such asprocessor 1423 and 1433.

A storage device may also store instructions, instructions, such assource code or binary code, for performing the techniques describedabove. A storage device may additionally store data used and manipulatedby the computer processor. For example, a storage device in a videoencoder 1420 or a video decoder 1430 may be a database that is accessedby computer system 1423 or 1433. Other examples of storage deviceinclude random access memory (RAM), read only memory (ROM), a harddrive, a magnetic disk, an optical disk, a CD-ROM, a DVD, a flashmemory, a USB memory card, or any other medium from which a computer canread.

A memory or storage device may be an example of a non-transitorycomputer-readable storage medium for use by or in connection with thevideo encoder and/or decoder. The non-transitory computer-readablestorage medium contains instructions for controlling a computer systemto be configured to perform functions described by particularembodiments. The instructions, when executed by one or more computerprocessors, may be configured to perform that which is described inparticular embodiments.

Also, it is noted that some embodiments have been described as a processwhich can be depicted as a flow diagram or block diagram. Although eachmay describe the operations as a sequential process, many of theoperations can be performed in parallel or concurrently. In addition,the order of the operations may be rearranged. A process may haveadditional steps not included in the figures.

Particular embodiments may be implemented in a non-transitorycomputer-readable storage medium for use by or in connection with theinstruction execution system, apparatus, system, or machine. Thecomputer-readable storage medium contains instructions for controlling acomputer system to perform a method described by particular embodiments.The computer system may include one or more computing devices. Theinstructions, when executed by one or more computer processors, may beconfigured to perform that which is described in particular embodiments

As used in the description herein and throughout the claims that follow,“a”, “an”, and “the” includes plural references unless the contextclearly dictates otherwise. Also, as used in the description herein andthroughout the claims that follow, the meaning of “in” includes “in” and“on” unless the context clearly dictates otherwise.

Although exemplary embodiments of the invention have been described indetail and in language specific to structural features and/ormethodological acts above, it is to be understood that those skilled inthe art will readily appreciate that many additional modifications arepossible in the exemplary embodiments without materially departing fromthe novel teachings and advantages of the invention. Moreover, it is tobe understood that the subject matter defined in the appended claims isnot necessarily limited to the specific features or acts describedabove. Accordingly, these and all such modifications are intended to beincluded within the scope of this invention construed in breadth andscope in accordance with the appended claims.

The invention claimed is:
 1. A method of decoding a bitstream by adecoder, comprising: (a) receiving said bitstream indicating how acoding tree unit was partitioned into coding units according to aquadtree plus multi-type tree structure that allows a square parent nodeto be split with a quaternary tree partitioning that splits said squareparent node in half in both horizontal and vertical directions to definequadtree leaf nodes that are square in shape each of which are the samesize, wherein said quadtree plus multi-type tree structure allows one ofsaid quadtree leaf nodes to be split based upon one selected from agroup consisting of, a symmetric binary tree partitioning that splitsone of said quadtree leaf nodes of said quaternary tree partitioning inhalf in either a horizontal direction or a vertical direction resultingin two blocks that together are the same size as child nodes, and (ii)an asymmetric tree partitioning that splits one of said quadtree leafnodes of said quaternary tree partitioning in either a horizontaldirection or a vertical direction resulting in a plurality of blocksthat have different sizes as child nodes; (b) wherein said child nodesas a result of said symmetric binary tree partitioning are allowed to befurther partitioned by either or said symmetric binary tree partitioningand said asymmetric tree partitioning; (c) wherein said child nodes as aresult of said asymmetric tree partitioning are allowed to be furtherpartitioned by either or said symmetric binary tree partitioning andsaid asymmetric tree partitioning; (d) identifying final coding units tobe decoded represented by leaf nodes of the quadtree plus multi-typetree structure; and (e) decoding the identified final coding units usinga decoding process.
 2. A computer readable storage device storing abitstream of compressed video data for decoding by a decoder, thebitstream comprising: (a) said bitstream indicating how a coding treeunit was partitioned into coding units according to a quadtree plusmulti-type tree structure that allows a square parent node to be splitwith a quaternary tree partitioning that splits said square parent nodein half in both horizontal and vertical directions to define quadtreeleaf nodes that are square in shape each of which are the same size,wherein said quadtree plus multi-type tree structure allows one of saidquadtree leaf nodes to be split based upon one selected from a groupconsisting of, (i) a symmetric binary tree partitioning that splits oneof said quadtree leaf nodes of said quaternary tree partitioning in halfin either a horizontal direction or a vertical direction resulting intwo blocks that together are the same size as child nodes, and (ii) anasymmetric tree partitioning that splits one of said quadtree leaf nodesof said quaternary tree partitioning in either a horizontal direction ora vertical direction resulting in a plurality of blocks that havedifferent sizes as child nodes; (b) wherein said child nodes as a resultof said symmetric binary tree partitioning are allowed to be furtherpartitioned by either or said symmetric binary tree partitioning andsaid asymmetric tree partitioning; (c) wherein said child nodes as aresult of said asymmetric tree partitioning are allowed to be furtherpartitioned by either or said symmetric binary tree partitioning andsaid asymmetric tree partitioning; (d) said bitstream including finalcoding units to be decoded represented by leaf nodes of the quadtreeplus multi-type tree structure; and (e) said identified final codingunits of said bitstream suitable for a decoding process.
 3. A method ofencoding a bitstream by an encoder, comprising: (a) providing saidbitstream indicating how a coding tree unit was partitioned into codingunits according to a quadtree plus multi-type tree structure that allowsa square parent node to be split with a quaternary tree partitioningthat splits said square parent node in half in both horizontal andvertical directions to define quadtree leaf nodes that are square inshape each of which are the same size, wherein said quadtree plusmulti-type tree structure allows one of said quadtree leaf nodes to besplit based upon one selected from a group consisting of, (i) asymmetric binary tree partitioning that splits one of said quadtree leafnodes of said quaternary tree partitioning in half in either ahorizontal direction or a vertical direction resulting in two blocksthat together are the same size as child nodes, and (ii) an asymmetrictree partitioning that splits one of said quadtree leaf nodes of saidquaternary tree partitioning in either a horizontal direction or avertical direction resulting in a plurality of blocks that havedifferent sizes as child nodes; (b) wherein said child nodes as a resultof said symmetric binary tree partitioning are allowed to be furtherpartitioned by either or said symmetric binary tree partitioning andsaid asymmetric tree partitioning; (c) wherein said child nodes as aresult of said asymmetric tree partitioning are allowed to be furtherpartitioned by either or said symmetric binary tree partitioning andsaid asymmetric tree partitioning; (d) wherein final coding units areencoded represented by leaf nodes of the quadtree plus multi-type treestructure; and (e) wherein the identified final coding units are encodedusing an encoding process.